Aluminum block thread repair
 

Hi,
I would like recommendations for repairing the threads in a 1983 380 SEC 116 V8 aluminum block. The block has some threads already repaired with helicoils and two that appear to be timeserts. Two of the helicoils partially unwound during disassembly and I am considering repairing with Helicoils or Timeserts. I will need to purchase a kit for
either one. Does anyone have a recommendation?
Thanks, Bob

I use Helicoils (usually 30 mm dia.) in my work and have had good luck with them. Be sure that when you drill the new hole that it is square (aligned in both planes) with the old one. Check with a machine shop that works with aluminum about the drill bit. Standard bits must be reground to a different angle when drilling non-ferrous metals like brass. I don't work with aluminum so I don't know if bits must be altered for it.

Hopefully your helicoils were installed correctly and you can just screw in new inserts. Timeserts are supposed to be drilled using a guide plate to keep the hole angle right (some of those holes are not square with the deck of the block on the engine), and that plate costs $342 and the inserts $70 something, if I rememember right. Use google and search for Timesert.

That job isn't a DIYer. You need a drilling jig($400) to drill the holes at the correct angle! Also you need a special starting tap to guide the tapping process.

Doesn't matter if you use "Timeserts" or "heli-coils" you still need the drilling jig.

Isn't there a type of compound (glue) suggested for use with the coil inserts to lock them into place and prevent backing out?

Could you just unwind the helicoils the rest of the way, and put the exact same size back in?

Just an idea...

hello

i agree with mbdoc this type of repair needs to be square and straight. in drilling a hole by hand you will get out of round holes, crooked holes, oversize holes and all sorts of pure ugly.

now if you were on a cast iron block you could use a mag drill but.....

as for the tapping you need tap holder to start the tap straight. it's kind of a tower that holds the tap&handle perpendicular to the surface being tapped. also don't use a 4 flute tap and don't buy a hanson tap from ACE hdwre. they are for chasing threads not really for tapping because they are not High Speed Steel and a 4 flute tap is nothing more than a hole plugger).

what you need is the right equipment but most DIY don't have all the right stuff. you didn't say directly but it appears that some of the previous kits weren't installed correctly.

i'd let a wrench do this one. he has the equipment and special tools needed for the job.

if you do, decide to do this job a little trick is to use a can of foamy shave creme. after you pack off the block set up a catch area by taping up a wall around the hole you're working on and fill it with foam shave creme. the wall will keep you from throwing any shavings that the foam doesn't get.

good luck
craig

That isn't what MBDOC is saying. It is not enough to get the holes perpendicular. They are angled, and MB makes a special jig to get the angles right.

I would recommend the TimeSerts rather than Helicoil on parts that will be removed again. Helicoil is fine one-shot, but I've heard of too many problems with them unscrewing with the bolt when something had to come off again.

The Timesert is swaged in place, plus it's a solid cylinder of steel, not must a "fat thread". The only drawback is that you must have enough material to drill out, cut the shoulder, and insert the TimeSert. If you don't have the space, use the Helicoil.

The jig for drilling and tapping the aluminum block is REQUIRED -- else the head bolts won't go in. Big trouble.... The repair, however, if done correctly is permanent, and the later blocks come with TimeSert or similar inserts, I think, not bare aluminum. Sooner or later a bare steel bolt in an aluminum block is going to remove the thread from the block...

Peter

Aluminum Block Repair
 

Thanks to all for the assistance, much appreciated! Today I pulled/picked out the old threads in the three holes I need to repair.
All are in the center of the block where the holes are tapped on an angle. I think I will ask a friend to make a jig similar to the drilling plate in the manual ( Friend has a small machine shop in garage) . The manual shows the proper angle. I also decided to go with Timeserts over Helicoils for no other reason than the shop selling them had both and recommended the Timeserts and I have had several recommendations for the Timeserts.
Thanks again, Bob